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| Titel |
The role of Lake Dongting in regulating the sediment budget of the Yangtze River |
| VerfasserIn |
Shi-bao Dai, Shi-lun Yang, Jun Zhu, Ang Gao, Peng Li |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 9, no. 6 ; Nr. 9, no. 6 (2005-12-31), S.692-698 |
| Datensatznummer |
250007148
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| Publikation (Nr.) |
 copernicus.org/hess-9-692-2005.pdf |
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| Zusammenfassung |
| Lake Dongting, the second largest freshwater lake in China and located in the
middle reaches of the River Yangtze catchment, was formed at the beginning of
the Holocene period by sea level rise and has varied in size with changes in
local weather patterns. The sedimentation rate in Lake Dongting during the
Holocene is about 50×106 m3 yr-1, or
80×106 t yr-1 (a sand bulk density of
1.6×103 kg m-3), given the sediment deposition rate as
10 mm yr-1 and the average lake size as 5000 km2. By comparing the
sediment import and export, it is estimated that the sediment deposition rate
of Lake Dongting was 110.6×106 t yr-1 from 1956 to 2003.
Siltation and raised embankments reduced the size of the lake and its
capacity to accommodate floods. The sediment delivery ratio (SDR) of the
middle and lower Yangtze is about 0.92 (total sediment output divided by
total sediment input) given that the total sediment supply into the middle
and lower Yangtze is 455.1×106 t yr-1 and the total sediment
discharge into the sea is 419×106 t yr-1. Therefore, if it
were not for Lake Dongting, the sediment flux at Datong would be
73.6×106 t yr-1 (80×106 t yr-1×0.92)
more, an increase of 27% during the Holocene and an increase of 26% to
101.75×106 t yr-1 from 1956 to 2003. Historically, Lake
Dongting had a considerable influence in regulating the sediment budget of
the Yangtze. However, afforestation and the construction of large dams, such
as the Three Gorges Dam, reduced significantly the sediment deposition in
Lake Dongting. In 2003, the completion of the Three Gorges Dam and the
subsequent impoundment of water reduced the sediment input from the Yangtze
and net deposition in Lake Dongting dropped to 25% and 18% of the mean
values of the historic records (1956-2003). During the same period, the
amount of sediment deposited in Lake Dongting was only 10% of the sediment
discharge at Datong. The influence of the sediment deposited in Lake Dongting
on the sediment flux to the sea from the Yangtze has fallen since the
completion of the Three Gorges Dam and will be further reduced in future. The
evolution of the relationship between Lake Dongting and the Yangtze is a
compound result of human impacts coupled with natural self-adjusting
processes in the river system. |
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